getimage.php

<?php
try {
	$posted_id = $_GET['unique_id'];

	$conn = new Mongo;
	$db = $conn->thundergallery;
	$grid = $db->getGridFS();
	$file = $grid->findOne(array('unique_id' => $posted_id));
	echo $file->getBytes();
	exit;
	$conn->close();
}catch(MongoConnectionException $e){
	die('Error connecting to MongoDB server');
}catch(MongoException $e){
	die('Error: ' . $e->getMessage());
}
?>

index.php

<?php 
	require 'lib.php';
	$connect = new Gallery();
	$uniqueID = $connect->uniqueID();
	$getImages = $connect->getImage();
?>

lib.php

<?php
	class Gallery extends Mongo{
		
		public $unique_id;
		
		function uniqueID(){
			$db = $this->thundergallery;
			$collection = $db->images;
			$cursor = $collection->find();
			foreach ($cursor as $obj) {
				$unique_id = $obj['unique_id'];
				echo " <a href='getimage.php?unique_id=".$unique_id."' class='lightbox_trigger'><img height='100px' width='100px' src='getimage.php?unique_id=".$unique_id."'></a> ";
			}
		}
	
		function getImage(){
			global $unique_id;
			$unique_id = $_GET['unique_id'];
			$db = $this->thundergallery;
			$grid = $db->getGridFS();
			$file = $grid->findOne(array('unique_id' => $unique_id));
			//echo $file->getBytes();
			exit;
			$conn->close();
		}
	
	}
?>